It is desirable to provide a comfortable environment for a child seated in a seat, for example in developing a child-care instrument.
Ventilation is one of the factors providing the comfortable environment for the child. In summer or a humid season, the seat preferably has good ventilation to provide coolness for the child seated therein. Meanwhile, in winter or on cold and windy days, the seat preferably holds warmth by preventing a draft.
A child-care instrument satisfying the above requirements is the subject matter of the above mentioned U.S. application Ser. No. 10/305,925 as well as the corresponding Japanese Patent Application No. 2002-164436, filed on Jun. 5, 2002 and published in Japanese Laying-Open No. 2003-175827 on Jun. 24, 2003, which is owned by the same Assignee as the present application. In view of the publication date, this reference is not prior art against the present application, and it is cited herein merely as background information and as a starting point for the further development of the present invention.
An essential point of the invention disclosed in the above application is described with reference to present FIGS. 1 and 2. A wall forming a seat of the child-care instrument, a backrest wall, for example comprises a first plate member 1 and a second plate member 2 which are arranged to be overlapped. The first plate member 1 has many first openings 3 penetrating in the thickness direction and the second plate member 2 has many second openings 4 penetrating in the thickness direction.
The second plate member 2 is provided so as to be relatively changeable in position between a first position (a state shown in FIG. 2) in which the first openings 3 and the second openings 4 are aligned and a second position (a state shown in FIG. 1) in which positions of the first openings 3 and the second openings 4 are shifted.
According to the child-care instrument provided with the above constitution, when the second plate member 2 is held in the first position (the state shown in FIG. 2), since the wind comes through the first and second aligned openings 3 and 4, good ventilation can be provided. Meanwhile, when the second plate member 2 is held in the second position (the state shown in FIG. 1), since the first and second openings 3 and 4 are shut down and the wind does not come through the openings, heat can be well retained.
However, there is a point to be improved in the child-care instrument having the above constitution. This is described with reference to FIGS. 3 and 4 hereinafter.
A seat of a child-care instrument shown in FIG. 3 comprises a seat plate 5 having through holes 7 and a backrest plate 6 having through holes 8. The backrest plate 6 can be reclined.
In order to simplify a constitution for implementing ventilation, a lapping plate 10 is a sheet of a flat plate integrally comprising a seat surface portion 11 facing the seat plate 5 and a back surface portion 12 facing the backrest plate 6. The seat surface portion 11 of the lapping plate 10 has through holes 13 which can be aligned with the through holes 7 of the seat plate 5, and the back surface portion 12 of the lapping plate 10 has through holes 14 which can be aligned with the through holes 8 of the backrest plate 6. The back surface portion 12 of the lapping plate 10 is connected to a rear end portion of the seat surface portion 11 such that it can be bent in order to follow a reclining operation of the backrest plate 6.
There is a problem that in the case of the lapping plate 10 integrally comprising the seat surface portion 11 and the back surface portion 12, the lapping plate 10 is not smoothly moved in the vertical direction because of existence of a bending point between both. When the bending point is constituted so as to have an accordion structure in order to avoid forming a sharp corner part, the corner part becomes too flexible and the movement of the back surface portion 12 cannot be transmitted to the seat surface portion 11. In order to avoid the above problem, it is thought that the bending point is formed of a hard portion having a configuration drawing a gentle circular arc, but even in such case, the following problems arise.
According to the seat shown in FIG. 3, the through holes 8 of the backrest plate 6 and the through holes 14 of the back surface portion 12 of the lapping plate 10 are aligned, and the through holes 7 of the seat plate 5 and the through holes 13 of the seat surface portion 11 of the lapping plate 10 are aligned. Then, it is assumed that a reclining angle of the backrest plate 6 is changed while this aligned state of the through holes is maintained. In FIG. 4, a state in which the backrest plate 6 is relatively raised is shown by a solid line and a state in which it is reclined is shown by a dotted line.
FIG. 4 shows each member illustratively, in which a bending point and an end portion are made to be noticeable in order to easily understand its movement. More specifically, the seat plate 5 has a front point 16, and the backrest plate 6 has a rear point 17. The backrest plate 6 is reclined in such a manner that a connection point 15 becomes a bending center. The seat surface portion 11 of the lapping plate 10 has a front point 19, and the back surface portion 12 has a rear point 20. The back surface portion 12 is reclined in such a manner that a connection point 18 becomes a bending center. In the state shown by the solid line in FIG. 4, as a matter of convenience, a height of the rear point 17 of the backrest plate 6 is shown so as to be almost the same as that of the rear point 20 of the back surface portion 12, and a front position of the front point 16 of the seat plate 5 is shown so as to be almost the same as that of the front point 19 of the seat surface portion 11.
As the backrest plate 6 is reclined, the rear point 17 of the backrest plate 6 and the rear point 20 of the back surface portion 12 are both moved along a circular arc 21 in which the connection point 15 is the center of curvature and a length of the backrest plate 6 is a radius. In the state shown by the dotted line in FIG. 4, the connection point 18 between the back surface portion 12 and the seat surface portion 11 is positioned on a circular arc 22 in which the rear point 20 of the seat surface portion. 11 is the center of curvature and a length of the seat surface portion 12 is a radius. Therefore, as shown in FIG. 4, the connection point 18 is shifted by L before-and-after the reclining operation of the backrest plate 6.
Similarly, since the front point 19 of the seat surface portion 11 is positioned on a circular arc 23 in which the shifted connection point 18 is a bending center, it is displaced before-and-after the reclining operation of the backrest plate 6.
The following problems arise because of the above positional displacement. That is, as the backrest plate 6 is reclined in the state in which the through holes are aligned shown in FIG. 3, although the aligned state of the through holes 8 of the backrest plate 6 and the through holes 14 of the back surface portion 12 is maintained after the reclining operation, the positions of the through holes 7 of the seat plate 5 and the through holes 13 of the seat surface portion 11 are displaced after the reclining operation, so that the ventilation is inhibited. On the contrary, as the backrest plate 6 is reclined in the state in which the through holes 7 of the seat plate 5 and the through holes 13 of the seat surface portion 11 are shut down, positions of both through holes could coincide with each other despite the intention.